Dec 17 2008

Researchers bring mind-controlled robotic limbs a few steps closer

Even the most fertile science fiction imagination might not see a link between the behaviour of insects and the development of lifelike robotic limbs, but that is the straightforward mathematical reality of research underway in the UTS Faculty of Engineering and Information Technology.

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PhD student Rami Khushaba knows it takes some explaining, but the analysis of the behaviour of social insects like ants is helping find the best way to tap into the body’s electrical signals, so that a robotic prosthetic device can be operated like a flesh and blood limb, just by thinking about it.

“I don’t think the crossover from science fiction to science reality is that far away now,” Rami said. “It has been known for some time that human muscle activity, known as the Electromyogram (EMG), carries the distinct signature of the voluntary intent of the central nervous system.

“These so-called myoelectric signals are already being used to control prosthetic devices, but there is a lot of refining to do before a robotic arm will respond instantaneously and accurately to the intention to move.

“Right now the best that can be done is a few simple tasks with rather unsatisfactory performance, due to poor signal recognition and the high computational cost that leads to extra time delays.

“Improvement in analysing the myoelectric signals will spur improvement of the hardware, and that’s where our work is directed.”

Supervised by Dr Adel Al-Jumaily and Dr Ahmed Al-Ani of the School of Electrical, Mechanical and Mechatronic Systems, Rami is developing the mathematical basis for identifying what biosignals relate to particular arm movements and where electrodes should be placed to achieve the optimum result.

“This project presents novel ‘swarm intelligence’ based algorithms to tackle many of the problems associated with the current myoelectric control strategies,” Rami said.

“The way the members of a colony of ants will interact to achieve goals like finding food is metaphor that can be expressed in algorithms that are powerful tools for pattern recognition.

“Current methods for capturing biosignals on the forearm can involve mounting up to 16 electrodes on the skin, generating a vast quantity of data to be processed. We have already demonstrated that applying swarm logic will both simplify that set-up and achieve significantly better results.

“Applying the algorithms on 16-channel EMG datasets from six people found patterns that made it clear only three surface electrodes were actually needed.

“These few electrode positions achieved 97per cent accuracy in capturing the crucial biosignals for movement. This significantly reduced the number of channels to be used for a real time problem, thus reducing the computational cost and enhancing the system’s performance.

“The result was confirmed on a second dataset consisting of eight channels of EMG data collected from the right arm of thirty normally limbed subjects (twelve males and eighteen females).

“We hope one accuracy will lead to another and it will be the very near future when amputees, who can still imagine moving a lost limb, will have access to a device that can truly respond to their intentions.”


Nov 14 2008

Self-propelled microbots

The 1966 science-fiction movie Fantastic Voyage famously imagined using a tiny ship to combat disease inside the body. With the advent of nanotechnology, researchers are inching closer to creating something almost as fantastic. A microscopic device that could swim through the bloodstream and directly target the site of disease, such as a tumor, could offer radical new treatments. To get to a tumor, however, such a device would have to be small and agile enough to navigate through a labyrinth of tiny blood vessels, some far thinner than a human hair.

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Researchers at the École Polytechnique de Montréal, in Canada, led by professor of computer engineering Sylvain Martel, have coupled live, swimming bacteria to microscopic beads to develop a self-propelling device, dubbed a nanobot. While other scientists have previously attached bacteria to microscopic particles to take advantage of their natural propelling motion, Martel’s team is the first to show that such hybrids can be steered through the body using magnetic resonance imaging (MRI).

To do this, Martel used bacteria that naturally contain magnetic particles. In nature, these particles help the bacteria navigate toward deeper water, away from oxygen. “Those nanoparticles form a chain a bit like a magnetic compass needle,” says Martel. But by changing the surrounding magnetic field using an extended set-up coupled to an MRI machine, Martel and his colleagues were able to make the bacteria propel themselves in any direction they wanted.

The bacteria swim using tiny corkscrewlike tails, or flagella, and these particular bacteria are faster and stronger than most, says Martel. What’s more, they are just two microns in diameter–small enough to fit through the smallest blood vessels in the human body. The team treated the polymer beads roughly 150 nanometers in size with antibodies so that the bacteria would attach to them. Ultimately, the researchers plan to modify the beads so that they also carry cancer-killing drugs.

“I think nature has provided an excellent solution to how to make small things swim,” says Bradley Nelson, a professor at ETH Zurich, who has researched the use of artificial flagella. “What’s interesting about Sylvain’s work is that he’s actually using nature to do it and not just learning from it.”

Last year, Martel and his group published research in the journal Applied Physics Letters detailing how they used an MRI machine to maneuver a 1.5-millimeter magnetic bead with a bacteria propeller through the carotid artery of a living pig at 10 centimeters per second. The researchers’ latest work, presented at the IEEE 2008 Biorobotics Conference last week, shows that they can track and steer microbeads and bacteria or bacteria alone through a replica of human blood vessels using the same approach. The group has carried out similar experiments in rats and rabbits, according to Martel.

Source Technology Review